Plural electrode unit electron tube



Aug- 23, 966 v R. A. BONNETTE ETAL 3,

I PLURAL ELECTRODE UNIT ELECTRON TUBE Fi led May 5, 1964 2 Sheets-Sheetl INVENTORS HIEHFIRD H. Bowman-e i'fi-mmns E DEEEHN 3, 1966 R. A.BONNETTE ETAL 3,268,760

PLURAL ELECTRODE UNIT ELECTRON TUBE Filed May 5, 1964 2 Sheets-Sheet 2INVENTORS RIEHHBD F1. BEINNET'IE 3;: TI-mMas E. DEEEBN p 3,268,769Patented August 23, 1965 3,268,760 PLURAL ELECTRQDE UNIT ELECTRQN TUBERichard A. Bonnette, New Providence, N.J., and Thomas Edward Deegan,Brewster, N.Y., assignors to Radio Corporation of America, a corporationof Delaware Filed May 5, 1964, Ser. No. 364,932 8 Claims. (Cl. 313-296)This invention relates to plural electrode unit electron tubes, andparticularly to plural electrode unit electron tubes wherein theelectrode units have matched electrical characteristics.

By electrode unit is meant a plurality of cooperating electrodesproviding the electrical characteristics of a triode or pentode electrontube, or the like. Several electrode units may be provided within asingle electron tube envelope. By matched electrical characteristics ismeant that there is a preselected relationship between the electricalcharacteristics of the different electrode units. Generally, the desiredrelationship is that the electrical characteristics of the electrodeunits be substantially identical.

This invention further relates to plural electrode urn't tubes whereinone or more electrodes are common to, or shared by, all the electrodeunits.

Heretofore, two modes of construction have been generally used in themanufacture of plural electrode unit electron tubes having commonelectrodes.

According to one mode of construction, a single electrode, usually thecathode electrode, is mounted between and extends through two or moreaxially spaced pairs of spacer plates. Mounted between each of the pairsof spacer plates, and in surrounding relation with a portion of thecathode, are a plurality of concentric electrodes. Each cathode portionand the concentric electrodes disposed there around constitute anelectrode unit.

A disadvantage of this mode of constnuction is that electron tubes madein this fashion are complicated and difiicult to assemble, and areexpensive.

According to another mode of construction, only one pair of spacerplates is used, and the electrodes of each electrode unit are grouped inseparate sectors with respect to the common electrode. Thus, forexample, in one type of electron tube including a pair of matchedtriodes, a single rectangular cathode is mounted between a pair ofspacer plates, and a grid electrode and an anode are mounted between thespacer plates on opposite sides of the rectangular cathode. Each cathodeside and the grid and anode opposite that side constitute a triode unit.

A disadvantage of this mode of constnuction, however, is that it hasbeen found extremely difficult to provide the different electrode unitswith electrode spacings which are sufficiently similar so as to providematched electrical characteristics. One reason for this difficulty isthat any inaccuracy in the location of the common electrode generallycauses the common electrode to be closer to one of the electrode unitsand correspondingly further from another of the electrode units. Thus,the amount of mismatch between the electrode spacings of these two unitsis twice the amount of the inaccuracy of location of the commonelectrode.

An object of this invention is to provide a plural electrode unitelectron tube having one or more electrodes common to the electrodeunits, said electrode units being electrically matched, and said tubebeing relatively simple and inexpensive to fabricate.

A further object of this invention is to provide a plural electrode unitelectron tube having one or more electrodes common to the units, whereinall the electrodes of the units are mounted between a common pair ofspacer plates, and wherein the matching of the electricalcharacteristics of the electrical units is relatively unaffected, ascompared with prior art tube constructions, by inaccuracies in thelocation of the various electrodes of the several electrode units.

For achieving the objects of this invention in accordance with oneembodiment of the invention, a duel electrode unit electron tube may beprovided comprising an elongated cathode mounted between a pair ofspacer plates. Disposed around each of two longitudinal portions, suchas each longitudinal half of the cathode, are two or more electrodes.Each cathode longitudinal portion and the electrodes disposed therearound form an electrode unit. Except for the cathode, and any otherelectrodes common to both electrode units, support means for theelectrodes of each electrode unit extend past the other electrode unit.The support means of all the electrodes of both electrical units aremounted between a single pair of spacer plates.

A more detailed description of an embodiment of this invention, and adiscussion of advantages of the invention follow in connection with adescription of the drawings, wherein:

FIGS. 1 and 2 are schematic end views showing the relative spacings ofthe electrodes of a prior art triode electron tube;

FIG. 3 is a view similar to FIGS. 1 and 2 but showing a prior art doubletriode;

FIG. 4 is a view in perspective with the envelope broken away of anelectron tube embodying the invention and showing the electron tubemount;

FIG. 5 is an exploded view, in perspective, of the plural electrode unitelectron tube mount of FIG. 4, and

FIG. 6 is a series of figures which, when taken together, show thecathode and grid arrangement of another plural electrode unit electrontube which may be made according to this invention, each pair of FIGURES6a-6l1, 60-641, 6e-6f, and 6g-6h, showing, in side elevation and planview, respectively, the arrangement of the lateral wire helix of each ofthe electron tube gride electrodes.

FIGS. 1 and 2 show, in schematic form, the relative dispositions of theelectrodes of a conventional triode comprising a rectangular cathode 1d,a .grid 12 including a pair of side rods 14 and a lateral wire helix 16wound around and secured to the side rods, and a box-like anode 18. Inthe tube shown in FIG. 1, the electrodes are perfectly coaxial, and thespacing between the various electrodes on each side of the tube are thesame. In the tube shown in FIG. 2, however, the cathode 10 is displaced(shown greatly exaggerated) from the center line of the tube, as occurs,for example, due to inaccuracies in the spacer plates used to positionthe electrodes, and the electrode spacings on one side of the tube aredifferent from the spacings on the other side of the tube.

Although different electrode spacings provide diflierent electricalcharacteristics, as known, the electrical characteristics of the tubesshown in FIGS. 1 and 2 will be relatively matched. This is because thetube electrodes are in surrounding relation with respect to one anotherand the effect on the tube electrical characteristics of the decreasedgrid to cathode spacing on one side of the tube shown in FIG. 2 islargely compensated for by the effect of the increased grid to cathodespacing on the other side of the tube.

FIG. 3 shows, schematically, the relative dispositions of the electrodesof a prior art double triode, the cathode electrode 20 being shown(greatly exaggerated) misaligned with respect to the grids 22 and 24 andthe anodes 26 and 28 of each electrode unit A and B, respectively.Because the grid and anode of each electrode unit are disposed on oneside only of the cathode 20, the compensating effect provided byelectrodes which surround a common cathode (as described in connectionwith the tubes shown in FIGS. 1 and 2) is not present in the tube shownin FIG. 3. Hence the difference in the cathode to grid spacing of eachelectrode unit caused by the mis-alignment of the cathode 20 causessusbtantial mismatching between the electrical characteristics of thetwo units.

FIG. shows a mount assembly of a double triode unit made according tothis invention. The mount assembly comprises a stem assembly 32 having aplurality of leads 33 therethrough to which are welded the ends ofelectrodes of a cage assembly 34. Each longitudinal half of cageassembly 34 is a separate triode unit C and D. Cage assembly 34comprises a pair of spacer plates 36 and 38 between which all of theelectrodes of each triode unit C and D (see FIG. 4) are mounted,extending ends of the electrodes extending through spaced apertures inthe spacer plates 36 and 38.

Mounted between the spacer plates 36 and 38 and com mon to both triodeunits C and D is an elongated rectangular cathode 40. The cathode iscoated over substantially its entire length between the spacer plates 36and 38 with a known electron emitting material, such as a combination ofstrontium and barium carbonates. The electrodes of each electrode unit Cand D have electron affecting portions concentric with only one-half thelength of the cathode between the spacer plates.

Triode unit C comprises a control grid 42 including a pair of side rods44 and a lateral wire helix 46 wound around and secured to a portion ofthe side rods. The ends of the side rods 44 extend through apertures 48in the spacer plates 36 and 38. Side rods 44 are disposed opposite thenarrow sides of rectangular cathode 40 and in this position, as known,have substantially no effect on the electrons emitted from the cathode.The electron affecting or controlling portion of control grid electrode42 is the lateral wire helix 46 wound around the side rods and disposedaround the cathode. As shown in FIG. 5, the lateral wire helix 46 ofgrid 42 is disposed around only the upper half of the cathode. Thus,only electrons emitted from the upper half of cathode 40 are controlledby grid electrode 42.

Disposed around grid 42 (FIG. 4) is an anode 50. As shown in FIG. 5,anode 50 is substantially U-shaped in cross section, and has a pair ofwings or legs 52 extending laterally from the ends of sides 54 of theanode. The lower portions of sides 54 are cut-away leaving a furtherpair of legs 56. Extending tabs or ears 58 are provided at the ends ofthe legs 52 and 56 and sides 54 for receipt within apertures 59 in thespacer plates 36 and 38. The portions 60 of sides 54 of the anode 50 arethe electron receiving portions of the anode. Sides 54 of the anode 50are joined by connecting straps 66.

When mounted in the cage assembly 34, as shown in FIG. 4, the electrodereceiving portions 60 of the anode 50 are disposed opposite the lateralwire helix 46 of grid 42, and the support legs 52 and 56 extend betweenthe spacer plates 36 and 38. Ears 58 are received through the apertures59 in the spacer plates to provide the proper positioning of the anode50 with respect to the other tube electrodes. The connecting strap 66(not visible in FIG. 4) of the anode 50 are positioned opposite andoutside the side rods 44 of grid 42. Anode connecting straps 66 are thusshielded from the cathode 40 by the side rods and have substantially noaffect upon electrons emitted from cathode 40.

Triode unit D is similar to triode unit C except that the lateral wirehelix 46 (FIG. 5) of control grid 42' and the electron receivingportions 60' of anode 50 of this unit are disposed around the lower halfof the cathode 40. Side rods 44 of grid 42, as shown, are disposed in aplane through the axis of cathode 40 and the side rods 44 of grid 42 ofunit C, and side rods 44 are mounted in staggered relation with respectto the side rods 44 of grid 42. Anode 50' of triode unit D is identicalto anode 50 of triode unit C.

Avoidance of electrical coupling between the triode units C and D isachieved by disposing the support members of the electrodes of the twounits, with the exception of the common cathode 40, in positions wherethey have little or no afiect upon the electrons emitted from thecathode. The side rods 44 and 44' of control grids 42 and 42',respectively, are disposed opposite the narrow sides of the rectangularcathode 40. Since control grids are usually negatively biased, the siderods cut-off all electron emission from the narrow sides of the cathode;hence, the side rods 44, 44' have little or no effect upon theelectrical characteristics of the triode units.

The side straps 66, 66' of the anodes 50, 50' are disposed beyond theside rods 44, 44, and are shielded from the cathode 40. Legs 52, 52' ofeach anode 50, 50 extend outwardly from sides 54, 54' of the anodes, andas shown in FIG. 4, the legs 52, 52 of each anode 50, 50' are disposedoutside the electron receiving portions 60, 60 of the other anode 50',50.

For providing identical electrical characteristics of triode units C andD, the dimensions of the grid electrodes 42 and 42' and anode 50 and 50'of each triode unit C and D are made the same. Thus, when assembled intocage assembly 34 the portions of the lateral wire helix 46 of grid 42which extend parallel to the wide sides of rectangular cathode 40 lie inthe same surfaces as the corresponding portions of the lateral wirehelix 46 of grid 42. Also, the pitch of the turns of the lateral wirehelices 46, 46' and the diameter of the wires in the lateral wirehelices of the grids 42, 42 are the same. Also, the electron receivingportions 60, 60' of the anodes 50, 50' lie within the same surfaces whenthe anodes are assembled into the cage assembly.

The anodes 50, 50' are identical and may be used interchangeably. Also,because of the staggered relation of the side rods 44, 44 of the grids,the grids are also identical and may be used interchangeably. Theinterchangeability of the anodes and grids simplifies manufacture andstorage of the electron tube parts.

As mentioned the electrodes of each unit C and D are mounted between thesame pair of spacer plates 36 and 38. This provides a tube structureconsiderably less complicated and expensive than the prior art tubesdescribed above which provide separate spacer plate pairs for eachelectrode unit.

A further advantage of the tube construction shown in FIGS. 4 and 5 isthat inaccurate positioning of the various electrodes 40, 42, 42', and50, 50' with respect to one another has relatively little affect uponthe matching of the electrical characteristics of the triode units C andD. This is because the electrodes of each triode unit C and D are insurrounding relation with respect to one another, and the compensatingeffect of this relation, as described in connection with the tubes shownin FIGS. 1 and 2, is present in the tube shown in FIGS. 4 and 5. Also,any misalignment of the common cathode electrode 40 with respect to theaxis of the tube tends to cause similar changes in the grid to cathodespacing of each unit C and D, and the electrical characteristics of thetwo units tend to remain matched.

In FIG. 6 is shown a dual pentode, such pentodes having utility, forexample, in color demodulator circuits of color television receivers, asknown. For clarity, each pair of FIGS. 6a-b, 6c-d, 6e-f, 6g-h, show thearrangement of the lateral wire helix of one grid electrode.

The pentode comprises a common cathode 70 mounted between a pair ofspacer plates 72, only one of which is shown in FIG. 6. Surroundingcathode 70 is a first control grid 74 having a lateral wire helix 76(FIGS. 6ab). The helix 76 surrounds substantially the entire length ofthe cathode 70 between spacer plates 72. Disposed around grid 74 is ascreen grid 78 having a lateral wire helix 80 (FIG. 6c-d). The lateralwire helix 80 of grid 78 is coextensive with the lateral wire helix 76of first control grid 74.

Disposed around portions of grids 74 and 78, as shown in FIGS. 6ethrough 6h, are a pair of second control grids 84, 84'. Second controlgrid 84 has a lateral wire helix 86 disposed around the upper half ofthe lateral wire helix 80 of screen grid 78, and second control grid 84'has a lateral wire helix 86 disposed around the lower half of thelateral wire helix 80 of screen grid 78. The portions of lateral wirehelices 86, 85 opposite each of the wide sides of rectangular cathode7!) lie in the same surface.

Although not shown, two anodes, which may be identical to the anodes 5t50 shown in FIGS. 4 and 5 are provided. The anodes are mounted betweenthe spacer plates 72 so that the electron receiving portions (such asportions 60, 60' of anodes 50, 50) of the anodes are disposed adjacent adifferent one of lateral wire helices 86, 86' respectively, of the twosecond control grids 84, 84.

The dual pentode illustrated in FIG. 6 thus comprises a cathode 70common to both electrode units, a first control grid 74 common to bothelectrode units, a screen grid 78 common to both electrode units, andseparate second control grids 84, 84' and anodes for each electrodeunit. The various electrodes are in surrounding relation, and thecontrol grids 84, 84', and the anodes (not shown in FIG. 6); but whichmay be identical to the anodes 50, 50' shown in FIGS. 4 and 5 for eachunit are identical and interchangeable. This tube also, therefore,possesses advantages of economy of manufacture as well as electricalsimilarity of the two sections.

What is claimed is:

1. An electron discharge device comprising a pair of spacer plates and aplurality of electrodes, said electrodes including a cathode mountedbetween said spacer plates, a pair of grid electrodes each having anelectron controlling portion, the electron controlling portion of one ofsaid grids being disposed around one portion only of said cathode, theelectron controlling portion of the other of said grids being disposedaround another portion only of said cathode, each of said gridelectrodes having support means extending past the electron controllingportion of the other of said grid electrodes and mounted between saidspacer plates, and a pair of anodes mounted between said spacer plates,each of said anodes having an electron receiving portion adjacent to adifferent one only of the electron controlling portions of said pair ofgrids.

2. An electron discharge device comprising a pair of spacer plates and aplurality of electrodes, said electrodes including an elongated cathodemounted between said spacer plates, a pair of grid electrodes eachhaving electron controlling portions, the electron controlling portionsof one of said grids being disposed around one longitudinal portion onlyof said cathode, the electron controlling portions of the other of saidgrids being disposed around another longitudinal portion only of saidcathode, each of said grid electrodes having support means extendingpast the electron controlling portions of the other of said gridelectrodes and mounted between said spacer plates, and a pair of anodes,each of said anodes having electron receiving portions adjacent to adi'fierent one only of the electron controlling portions of said pair ofgrids, and each of said anodes having support means extending past theelectron receiving portions of the other of said anodes and mountedbetween said spacer plates.

3. An electron discharge device comprising a pair of spacer plates and aplurality of electrodes, said electrodes including an elongated cathodemounted between said spacer plates, a pair of grid electrodes eachhaving electron controlling portions, the electron controlling portionsof one of said grids being disposed around one half only of the lengthof said cathode between said spacer plates, the electron controllingportions of the other of said grids being disposed around the other halfonly of the length of said cathode between said spacer plates, theelectron controlling portions of each of said grids lying in commonsurfaces, each of said grid electrodes having support means extendingpast the electron controlling portions of the other of said gridelectrodes and mounted between said spacer plates, and a pair of anodes,each of said anodes having electron receiving portions disposed around adifferent one of the electron controlling portions of said pair ofgrids, the electron receiving portions of said anodes lying in commonsurfaces, and each of said anodes having support means extending pastthe electron receiving portions of the other of said anodes and mountedbetween said spa-oer plates.

4. An electron discharge tube comprising a plurality of coaxialelectrodes and a pair of spacer plates, said electrodes including acathode mounted between said spacer plates, a first grid having alateral wire helix disposed around one longitudinal portion only of saidcathode between said spacer plates, a second grid having a lateral wirehelix disposed around another longitudinal portion only of said cathodebetween said spacer plates, each of said grids having side rodsextending past the lateral wire helix of the other of said grids andmounted between said spacer plates, and first and second anodes, each ofsaid anodes having an electron receiving portion adjacent to a differentone only of the lateral wire helices of said first and second grids, andeach of said anodes having support means extending past the electronreceiving portion of the other of said anodes and mounted between saidspacer plates.

5. An electron discharge tube comprising a plurality of coaxialelectrodes and a pair of spacer plates, said electrodes including acathode mountedbetween said spacer plates, a first grid having a lateralwire helix disposed around one half only of the length of said cathodebetween said spacer plates, a second grid having a lateral wire helixdisposed around the other half only of the length of said cathodebetween said spacer plates, portions of the lateral wire helices of saidfirst and second grids lying in common surfaces, each of said gridshaving side rods extending past the lateral wire helix of the other ofsaid grids and mounted between said spacer plates, and first and secondanodes, each of said anodes having electron receiving portions disposedaround a different one of the lateral wire helices of said first andsecond grids, the electron receiving portions of said anodes lying incommon surfaces, and each of said anodes having support means extendingpast the electron receiving portion of the other of said anodes andmounted between said spacer plates.

6. An electron discharge tube comprising a plurality of coaxialelectrodes and a pair of spacer plates, said electrodes including acathode mounted between said spacer plates, a first grid having alateral wire helix disposed around one half only of the length of saidcathode between said spacer plates, a second grid having a lateral wirehelix disposed around the other half only of the length of said cathodebetween said spacer plates, portions of the lateral wire helices of saidfirst and second grids lying in common surfaces, each of said gridshaving side rods extending past the lateral wire helix of the other ofsaid grids and mounted between said spacer plates, the side rods of saidgrids being in staggered relation and lying in a common plane, and firstand second anodes, each of said anodes having electron receivingportions disposed around a difierent one of the lateral wire helices ofsaid first and second grids, said electron receiving portions lying incommon surfaces, and each of said anodes having support means extendingpast and outside the electron receiving portions of the other of saidanodes and mounted between said spacer plates.

7. An electron discharge device comprising a plurality of coaxialelectrodes and a pair of spacer plates, said electrodes including acathode mounted between said spacer plates, first, second, third, andfourth grid electrodes, each of said grid electrodes comprising a pairof side rods mounted between said spacer plates and a lateral wire helixwound around at least portions of said side rods, the lateral wire helixof said first grid being displates, each of said anodes having electronreceiving 10 portions adjacent to a difierent one of said lateral wirehelices of said third and fourth grids.

8. An electron discharge device comprising a plurality of coaxialelectrodes and a pair of spacer plates, said electrodes including acathode mounted between said spacer plates, first, second, third, andfourth grid electrodes, each of said grid electrodes comprising a pairof side rods mounted between said spacer plates and a lateral Wire helixwound around at least portions of said side rods, the side rods of saidthird and fourth grid electrodes being staggered, the lateral wire helixof said first grid being disposed around substantially the entire lengthof said cathode between said spacer plates, the lateral wire helix ofsaid second grid being disposed around substantially the entire lengthof the lateral wire helix of said first grid, the lateral wire helix ofsaid third grid being disposed around one half only of the length of thelateral wire helix of said second grid, the lateral wire helix of saidfourth grid being disposed around the other half only of the length ofthe lateral wire helix of said second grid, portions of the lateral wirehelices of said third and fourth grids lying in common surfaces, theside rods of each of said third and fourth grids extending past thelateral wire helix of the other of said third and fourth grids, andfirst and second anodes, each of said anodes having electron receivingportions disposed around a different one of said lateral Wire helices ofsaid third and fourth grids, the electron receiving portions of saidanodes lying in common surfaces, and each of said anodes having supportmeans extending past and outside the electron receiving portions of theother of said anodes and mounted between said spacer plates.

References Cited by the Examiner UNITED STATES PATENTS 2,156,079 4/ 1939Beggs 313-298 2,187,591 1/1940 Manthorne 313-265 X 2,311,672 2/1943Leyan 3133 2,798,903 7/ 1957 Spencer 313-245 2,936,391 5/1960 Curry eta1. 3l3350 JOHN W. HUCKERT, Primary Examiner.

A. I. JAMES, Assistant Examiner.

1. AN ELECTRON DISCHARGE DEVICE COMPRISING A PAIR OF SPACER PLATES AND APLURALITY OF ELECTRODES, SAID ELECTRODES INCLUDING A CATHODE MOUNTEDBETWEEN SAID SPACER PLATES, A PAIR OF GRID ELECTRODES EACH HAVING ANELECTRON CONTROLLING PORTION, THE ELECTRON CONTROLLING PORTION OF ONE OFSAID GRIDS BEING DISPOSED AROUND ONE PORTION ONLY OF SAID CATHODE, THEELECTRON CONTROLLING PORTION OF THE OTHER OF SAID GRIDS BEING DISPOSEDAROUND ANOTHER PORTION ONLY OF SAID CATHODE, EACH OF SAID GRIDELECTRODES HAVING SUPPORT MEANS EXTENDING PAST THE ELECTRON CONTROLLINGPORTION OF THE OTHER OF SAID GRID ELECTRODES AND MOUNTED BETWEEN SAIDSPACER PLATES, AND A PAIR OF ANODES MOUNTED BETWEEN SAID SPACER PLATES,EACH OF SAID ANODES HAVING AN ELECTRON RECEIVING PORTION ADJACENT TO ADIFFERENT ONE ONLY OF THE ELECTRON CONTROLLING PORTIONS OF SAID PAIR OFGRIDS.